Exhaust from combustion engines creates a variety of environmental pollutants that must be removed from the exhaust stream in order to protect both public health and the environment. For automobiles, the 3-way catalyst has been used for decades to convert these chemicals, primarily carbon dioxide, nitrogen oxides, and unburned hydrocarbons into benign products, such as carbons dioxide, nitrogen, and water. However, as environmental regulations become more stringent, a higher loading of precious metals are required to purify the exhaust gases to the necessary levels.
One way to achieve higher conversion of pollutants and lower consumption of precious metals is to increase the efficiency of the catalyst. In the case of gasoline engines with 3-way catalysts, the efficiency of the catalytic converter could be enhanced if long chain hydrocarbons in the exhaust stream were broken down or cracked into smaller parafm or olefin molecules. In the case of some types of fuels (such as diesel fuel), the reduction of NOx is enhanced if fuel is added directly to the exhaust stream. Similar to the gasoline-based catalytic converter, the efficiency of the catalyst would be improved if the hydrocarbon molecules were broken down. This increase in efficiency would result in an overall decrease in emissions and precious metal consumption by the exhaust catalysts.
Catalytic cracking of crude oil using zeolite catalysts has been done in the petroleum industry for many years. In addition, thermal cracking of hydrocarbons is possible at high temperatures and pressures. The high pressure conditions needed for both of these reactions is not suitable for automotive applications.
There is therefore a need in the art for an improved process for the break down or cracking of hydrocarbons in an automotive application.